Earth moving machines known in the art are used for digging into the earth or rock and moving loosened work material from one place to another at a worksite. These machines and equipment typically include a body portion housing the engine and having rear wheels, tracks or similar components driven by the engine, and an elevated cab for the operator. The machines and equipment further include articulating mechanical arms or other types of linkages, such as Z-bar linkages, for manipulating one or more implements of the machine. The linkages are capable of raising and lowering the implements and rotating the implements to engage the ground or other work material in a desired manner. In the earth moving applications, the implements of the machines or other equipment are buckets provided with a beveled lip or blade on a base edge for moving or excavating dirt or other types of work material.
To facilitate the earth moving process, and to prolong the useful life of the implement, a plurality of tooth assemblies are spaced along the base edge of the implement and attached to the surface of the implement. The tooth assemblies project forward from the base edge as a first point of contact and penetration with work material, and to reduce the amount of wear of the base edge. With this arrangement, the tooth assemblies are subjected to the wear and breakage caused by repetitive engagement with the work material. Eventually, the tooth assemblies must be replaced, but the implement remains usable through multiple cycles of replacement tooth assemblies. Depending on the variety of uses and work material for the equipment, it may also be desirable to change the type or shape of the tooth assemblies to most effectively utilize the implement.
In many implementations, installation and replacement of the tooth assemblies may be facilitated by providing the tooth assemblies as a two-part system. The system may include an adapter that is attached to the base edge of the implement, a ground-engaging tip configured to be attached to the adapter, and a retention mechanism securing the tip to the adapter during use. The adapter may be welded, bolted or otherwise secured to the base edge, and then the tip may be attached to the adapter and held in place by the retention mechanism. The tip endures the majority of the impact and abrasion caused by engagement with the work material, and wears down more quickly and breaks more frequently than the adapter. Consequently, multiple tips may be attached to the adapter, worn down, and replaced before the adapter itself must be replaced. Eventually, the adapter may wear down and require replacement before the base edge of the implement wears out.
One example of a digging tooth assembly is illustrated and described in U.S. Pat. No. 4,949,481 to Fenner. The digging tooth for a bucket has a concave top surface and a convex bottom surface which intersect forming a forward cutting edge. Sidewalls connect the two surfaces and are concave having a moldboard shape. The rear portion of the tooth is provided with a mounting assembly for mounting the digging tooth to a bucket. The bottom surface continuously diverges from the forward cutting edge to the rear portion; whereas the top surface first converges then diverges from the forward cutting edge to the rear portion. The rear portion includes a shank receiving cavity with top and bottom walls that converge as the cavity extends forwardly within the tooth to give the cavity a triangular or wedge shape when viewed in profile.
An example of a loader bucket tooth is provided in U.S. Pat. No. 5,018,283 to Fellner. The digging tooth for a loader bucket includes a top surface having a concave configuration and a bottom surface having a flat forward portion and a convex rear portion. The flat forward portion and the top surface intersect to form a forward cutting edge. Sidewalls connect the two surfaces and are concave having a plowshare shape. The rear portion of the tooth is provided with a mounting assembly for mounting it to a bucket. The bottom surface continuously converges from the forward cutting edge to the rear portion; whereas the top surface first converges then diverges from the forward cutting edge to the rear portion. The rear portion includes a shank receiving cavity with bottom wall extending inwardly, and a top wall having a first portion extending approximately parallel to the bottom wall and a second portion angled toward the bottom wall and extending to a rounded front portion.
U.S. Pat. No. 2,982,035 to Stephenson provides an example of an excavator tooth having an adapter that attaches to the leading edge of a dipper body, and a tip that attaches to the adapter. The tip includes an upper surface and a lower surface that converge into a relatively sharp point, with the tip having a horizontal plane of symmetry. Upper and lower surfaces of the adapter have recessed central surfaces, with the upper central surface having a forward surface that diverges upwardly from the plane of symmetry and rounds into a forward surface of the adapter. The interior of the tip has corresponding planar surfaces that are received by the central surfaces of the adapter, and include forward surfaces diverging from the plane of symmetry as they approach a forward surface, with one of the forward surfaces of the tip abutting the forward surface of the adapter when the parts are appropriately assembled.
The implements as discussed may be used in a variety of applications having differing operating conditions. In loader applications, buckets installed on the front of wheel or track loaders have the bottom surfaces and base edges scrape along the ground and dig into the earth or pile of work material as the loader machine is driven forward. The forces on the tooth assembly as the bucket enters the pile push the tip into engagement with the corresponding adapter. The bucket is then raised and racked with the load of work material, and the loader moves and dumps the work material in another location. As the bucket is raised through the work material, force is exerted downwardly on the tooth assembly. With the combination of scraping and engagement with the work material, and in other types of bottom-wearing applications in which the bottom surface typically wears more quickly due to more frequent engagement with the work material, the wear material of the tip wears away from the front of the tip and from the bottom surface of the tip and adapter. The loss of wear material at the front of the tip converts the initially pointed front end of the tip into a rounded, blunt surface, similar to changing the hand from having extended fingers to having a closed fist. The worn down shape is less efficient at digging through the work material as the loader moves forward, though the tip may still have sufficient wear material to be used on the implement for a time before replacement.
In excavator applications and other types of top-wearing applications where the top surface typically wears more quickly due to more frequent engagement with the work material, the buckets engage and pass through the ground or work material at different angles than in bottom-wearing applications such as loader applications described above, and therefore cause wear material of the tooth assemblies to wear away in a different manner. An excavator device, such as a backhoe, initially engages the work material with the base edge and tooth assemblies oriented close to perpendicular with respect to the surface of the work material and generally enter the work material in a downward motion. After the initial penetration into the work material, the mechanical arm further breaks up the work material and collects a load of work material in the bucket by drawing the bucket back toward the excavator machine and rotating the bucket inwardly to scoop the work material into the bucket. The complex motion of the bucket causes wear at the tip of the tooth assembly during the downward penetration motion when the forces act to push the tip into engagement with the adapter. After the initial penetration, the bucket is drawn toward the machine and rotated to further in a scooping motion to break up the work material and begin to load the implement. During this motion, the forces initially act in a direction that is initially mostly normal to the top surface of the tooth assembly, and the work material passes over and around the top of the tooth causing wear on the top surface of the tooth. As the implement rotates further and is drawn through the work material, the forces and work material again act on the tip of the tooth to cause wear at the tip. As with the loader tooth assemblies, the excavator tooth assemblies wear down to less efficient shapes after repeated forays into the work material, but may still retain sufficient wear material for continued use without replacement. In view of this, a need exists for improved tooth assembly designs for loader and excavator implements that distribute the wear material such that the tips dig into the work material more efficiently as wear material wears away from and reshapes the tips until the tips ultimately must be replaced.